A standard center clamp 1′ as shown in FIG. 3 holds a workpiece 6 to be machined between two rods 4′ and 11′ so that the center clamp 1′ is an expensive and fairly tall device. Both the torque for angularly orienting the gripped workpiece 6 as well as the clamping force are the responsibility of respective drives at the outer end of the center clamp, that is outside a cup wheel 14′, while the gripping force passes parallel to an axis 4A′ through a force-transmitting element 2′ to the inner end and is there applied by a rocker arrangement to avoid deformations of the center clamp 1′ from the gripping force being exerted.
The disadvantage with this system is that such known center clamps are only limitedly pivotal as a result of their large size. Furthermore, they cannot normally be swung down into a standard cup wheel since the available space is relatively limited and the center clamp must not touch the edge of the cup wheel.
Hence when all the edges of the workpiece must be machined it is necessary that such center clamps be made axially relatively long in order that the necessary machining can take place on the far side of the grinding wheel, since there the required pivoting is possible without the possibility of contact. As a result of the long travel, machining with such a clamp is relatively slow and the long axial reach reduces the stiffness of the machining system, leading to sloppier machining results.